﻿using System;
using System.Collections.Generic;
using System.Linq;
using Wino.Core.Domain.Exceptions;

namespace Wino.Core.Domain.Models.Authorization;

public class GoogleAuthorizationRequest
{
    public const string RedirectUri = "google.pw.oauth2:/oauth2redirect";

    const string authorizationEndpoint = "https://accounts.google.com/o/oauth2/v2/auth";
    const string CodeChallangeMethod = "S256";

    public GoogleAuthorizationRequest(string state, string codeVerifier, string codeChallange)
    {
        State = state;
        CodeVerifier = codeVerifier;
        CodeChallange = codeChallange;
    }

    // Pre
    public string State { get; set; }
    public string CodeVerifier { get; set; }
    public string CodeChallange { get; set; }
    public string ClientId { get; set; }

    // Post
    public string AuthorizationCode { get; set; }

    public string BuildRequest(string clientId)
    {
        ClientId = clientId;

        // Creates the OAuth 2.0 authorization request.
        return string.Format("{0}?response_type=code&scope=https://mail.google.com/ https://www.googleapis.com/auth/gmail.labels https://www.googleapis.com/auth/userinfo.profile&redirect_uri={1}&client_id={2}&state={3}&code_challenge={4}&code_challenge_method={5}",
            authorizationEndpoint,
            Uri.EscapeDataString(RedirectUri),
            ClientId,
            State,
            CodeChallange,
            CodeChallangeMethod);
    }

    public void ValidateAuthorizationCode(Uri callbackUri)
    {
        if (callbackUri == null)
            throw new GoogleAuthenticationException(Translator.Exception_GoogleAuthCallbackNull);

        string queryString = callbackUri.Query;

        Dictionary<string, string> queryStringParams = queryString.Substring(1).Split('&').ToDictionary(c => c.Split('=')[0], c => Uri.UnescapeDataString(c.Split('=')[1]));

        if (queryStringParams.ContainsKey("error"))
            throw new GoogleAuthenticationException(string.Format(Translator.Exception_GoogleAuthError, queryStringParams["error"]));

        if (!queryStringParams.ContainsKey("code") || !queryStringParams.ContainsKey("state"))
            throw new GoogleAuthenticationException(Translator.Exception_GoogleAuthCorruptedCode + queryString);

        // Gets the Authorization code & state
        string code = queryStringParams["code"];
        string incomingState = queryStringParams["state"];

        // Compares the receieved state to the expected value, to ensure that
        // this app made the request which resulted in authorization
        if (incomingState != State)
            throw new GoogleAuthenticationException(string.Format(Translator.Exception_GoogleAuthInvalidResponse, incomingState));

        AuthorizationCode = code;
    }
}
